function myTime() {


    var startValue = document.getElementById("startTime").value;
    var endValue = document.getElementById("endTime").value;
    var intervalValue = document.getElementById("interval").value;
    var startDate = new Date("1/1/2015 " + startValue);
    var endDate = new Date("1/1/2015 " + endValue);
    var offset = intervalValue * 1000 * 60;
}

{ $match : { datetime : { $gt : startDate, $lt : endDate } } },
  {
   $group: {
    _id:{
    "$add": [
     { "$subtract": [
     { "$subtract": [ "$datetime", new Date(0) ] },
     { "$mod": [
    { "$subtract": ["$datetime" , new Date(0) ] },
    offset]}] },
    new Date(0)
     ]},
            Humidity: {$avg: "$humidity"},
            Temperature: {$avg: "$temperature"}

            },
            },

      { $project : { _id : 1 , Humidity : 1, Temperature: 1 } },
       // { $limit : 10 },
       { $sort :  {"_id":1, "Humidity":1, "Temperature": 1}}

function myTime() {
     var result = {}
     result.startValue = document.getElementById("startTime").value;
     result.endValue = document.getElementById("endTime").value;
     result.intervalValue = document.getElementById("interval").value;
     result.startDate = new Date("1/1/2015 " + startValue);
     result.endDate = new Date("1/1/2015 " + endValue);
     result.offset = intervalValue * 1000 * 60;
     return result;
   }

function getMongoObject(values) {
   return { "$match" : { "datetime" : { "$gt" : values.startDate, "$lt" : values.endDate } } },
        {
         "$group": {
        "_id":{
        "$add": [
         { "$subtract": [
         { "$subtract": [ "$datetime", new Date(0) ] },
         { "$mod": [
        { "$subtract": ["$datetime" , new Date(0) ] },
        values.offset]}] },
        new Date(0)
         ]},
        "Humidity": {$avg: "$humidity"},
        "Temperature": {$avg: "$temperature"}

        },
        },

       { "$project" : { "_id" : 1 , "Humidity" : 1, "Temperature": 1 } },
       // { "$limit" : 10 },
       { "$sort" :  {"_id":1, "Humidity":1, "Temperature": 1}}
}

var mongoValues = getTime();
var mongoObject = getMongoObject(mongoValues);

var startValue, endValue, intervalValue, startDate, endDate, offset;
function myTime() {
     startValue = document.getElementById("startTime").value;
     endValue = document.getElementById("endTime").value;
     intervalValue = document.getElementById("interval").value;
     startDate = new Date("1/1/2015 " + startValue);
     endDate = new Date("1/1/2015 " + endValue);
     offset = intervalValue * 1000 * 60;
   }